"There is nothing in the footage that contradicts the decision that manned re-entry of the mine is unsafe," the company chairman, Andy Coupe, said in a statement yesterday.

"The risks around re-entry do not centre around the conditions in the first part of the drift - which is what is shown in this footage.

"As has been previously documented, the significant re-entry risks are mainly beyond the part of the drift that has been explored by robot.

"As we have also previously stated, the mines rescue workers shown in the drift are in the first few metres. This is very different to the risks associated with being deep into the drift."

Mr Coupe went on to say no one, let alone media, politicians or other commentators with no mining expertise, could credibly assert that the footage showed that re-entry into the drift, let alone the mine itself, could be done safely.

Mr Coupe also denied any suggestion that Solid Energy had been involved in any cover-up.

"We ask once again, what possible motive would there be for the directors, two of whom are based in the Australian mining industry, to take such a course of action," Mr Coupe asked.

"Frankly the allegation lacks any credibility. The mine was not owned by Solid Energy at the time of the explosions. We have absolutely nothing to hide and would have nothing to gain by being less than transparent."

Worker was about 5m inside the drift - Mines Rescue Service

Mines Rescue Service has confirmed footage broadcast by RNZ on Friday showed one of its members about 5m inside the drift in March 2011, walking back towards the robot with the camera after clearing some wire in its way.

It said a container was placed at the entrance, and the worker walked through that before entering the drift.

The service's general manager, Trevor Watts, said the furthest anyone had gone inside the drift since the final explosion was about 300m.

A member went that far in October 2014 as part of work to complete a seal about 170m inside the drift.